Soaking pit and method of operating the same



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SOAKING PIT AND METHOD OF OPERATING THE SAME Filed Sept. 2l. 1943 2 Sheexs-Sheet 1 EJE-: l-

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Jan. 7, 1947. R, R SNOW SOAKING PIT AND METHOD 0F OPERATING THE SAME Filed Sept. 21, 1945 2 Sheets-Sheet 2 INVENTOR: /Q/C H10/QD /E 5A/0 ORNEY.

Patented Jan. 7, 1947 UNITED STATES PATENT OFFICE SOAKING PIT AND METHOD OF OPERATING THE SAME Application September 21, 1943, Serial No. 503,252

11 Claims.

This invention relates to an improvement in soaking pit furnaces and to a method of operating the same. These furnaces are commonly used to heat steel ingots to the proper temperature for rolling, and the invention is more particularly adapted to shallow soaking pits of the recuperative type, although not limited thereto. It is well known that the time necessary to heat ingots to the proper rolling temperature far exceeds the theoretical time based on the thermal conductivity of the steel. This is chiey due to the fact that the distribution of temperature throughout the pit is not uniform, and the rate of firing must be governed by the temperature of the hottest part of any ingot. In some furnaces the common method of heating the ingot is to fire the furnace for short periods and then soak the ingots for short periods alternately; and in other types of furnaces, the fuel rate is cut materially to prevent overheating and to allow continuous firing. In many instances the temperature rises rapidly at certain points in the ingot resulting in hot spots. In many types of furnaces the flame impinges directly on the pit walls or cover at one or more points, causing excessive damage to the refractory. Due to the poor distribution of heat throughout the furnace, the thermal efficiency of the furnace is low and the fuel consumption, therefore, high. Special types of soaking pit furnaces have been developed which improve the uniformity of temperature distribution, but do so at the expense of simplicity of design, and this results in increased repairs and less available operating time for the pit.

It is an object of this invention to accomplish more uniform temperature distribution throughout a soaking pit furnace of simple design by providing for better circulation of the hot gases.

A further object is to provide a soaking pit in which there is no direct impingement of the flames on either the pit walls or pit cover.

A still further object is to employ such an arrangement of ingots in the furnace and to control the velocity of the flame s that the hot gases will circulate freely in both a horizontal and vertical plane.

These and other objects will be more apparent after referring to the following description and attached drawings, in which:

Figure 1 is a plan view of the soaking pit of the invention showing the arrangement of the ingots and the direction of ow of the hot gases;

Figure 2 is a sectional view taken on the line II-II of Figure 1; v

Figure 3 is a view similar to Figure 1, but showing a circular soaking pit; and

Figure 4 is a sectional view taken on the line .IV- IV of Figure 3.

Referring more particularly to the drawings,

the reference numeral 2 indicates the walls of a soaking pit furnace. Located on opposite walls, near the top thereof, are two burners 4. Directly beneath these burners there may be provided ports 6 for admitting preheated air to the combustion chamber. Near the bottom of the walls, directly below the burners 4. are exit ports 8 for the waste gases. It will be seen that the burners and ports on the opposite walls are located adjacent diagonal corners, the distance between each of the burners and the adjacent corner being such that a row of ingots I0 may be placed along the adjacent wall without danger of direct flame impingement thereon. Any suitable pit cover of conventional design may be used on the pit.

The method of operating the soaking pit furnace is as follows:

Ingots I0 are placed around the periphery of the pit with a free space directly in front of the burners. The ingots are spaced from each other and the wall a distance sufficient to enable them to be grasped by means of ingot tongs, and to provide some circulation of gases completely around the ingot. A second group of ingots I2 may be placed in the center of the pit, this providing a path I4 of suflicient width to enable the hot gases to pass freely therethrough, and preferably at least two feet wide. The flow of gases is clearly shown in Figures 1 and 2 by means of arrows. The velocity of the flame and the stack draft are so regulated that the hot gases circulate freely in both vertical and horizontal planes through the path I4, the direction of flow being indicated by the arrows. With the ingots arranged as shown, at least one side of each ingot is directly exposed to the hot gases and the flames cannot impinge upon the pit walls.

The soaking pit of Figures 3 and 4 is quite similar to that disclosed in Figures 1 and 2, and the method of operating it is also similar. Burners 34 are located near the top of the pit wall 28 at two points diametrically opposite. Directly beneath the burners may be located preheated air ports I5. The burners are directed in essentially parallel planes with the distance between their center lines being suflicient to cause considerable circulation of the hot gases in a horizontal plane. Exit ports I8 are located near the bottom of the pit wall directly under each burner.

In operation, a plurality of ingots 20 are arranged around the circumference of the pit with a free space in front of each burner. A second group of ingots 22 may be placed in the center of the pit, this providing a path 24 similar to the path I4 in the rectangular soaking pit of Figure 1. The circulation of the heating gases is controlled in the same manner as the circulation of the hot gases in the rectangular soaking pit, the

direction of movement of the gases being clearly shown by the arrows in Figures 3 and 4.

While two embodiments of the invention have been shown and described, it will be apparent that other adaptations and modifications may be made without departing from the scope of the following claims.

I claim:

1. A shallow soaking pit furnace for reheating ingots comprising a pit, oppositely disposed fuel burners near the top of the walls of said pit and exit ports through said walls directly below said burners, the distance between the center lines of said burners being sufficient to cause circulation of the combustion gases in a horizontal plane, the flame from each of said fuel burners extending into said pit a sufficient distance from the adjacent wall to permit a row of ingots to be placed along the adjacent wall without danger of direct flame impingement thereon,

2. A shallow soaking pit furnace for reheating ingots comprising a pit, fuel burners disposed near the top of opposite walls of said pit and exit ports through said opposite walls adjacent the bottom thereof, the burner in each of said walls being disposed directly above said exit port, and at sufficient distance from the corner to permit a row of ingots to be placed along the adjacent wall `without danger of direct flame impingement thereon and the burner and exit port of one wall being disposed diagonally with respect to the burner and exit port of the other wall.

3. A shallow soaking pit furnace for reheating ingots comprising a pit, two oppositely disposed burners near the top of the walls of said pit, said burners being directed in essentially parallel planes with the distance between their center lines being sufficient to cause considerable circulation of the combustion gases in a horizontal plane, the flame from each of said fuel burners extending into said pit a sufficient distance from the adjacent wall to permit a row of ingots to be placed along the adjacent wall without danger of direct flame impingement thereon and exit ports for the waste gases directly below said burners near the bottom of the pit. the arrangement of said ingots being such that a free path is provided for circulation of hot gases both in a horizontal and vertical plane.

4. A shallow soaking pit furnace for reheating ingots comprising a pit, burners through two opposite walls of said pit near the top thereof and at a sufficient distance from two diagonally opposite corners to permit placing a row of ingots along the adjacent wall without danger of direct flame impingement thereon, and exit ports for the waste gases directly below said burners near the bottom of said pit, the arrangement of said ingots being such that a free path is provided for circulation of hot gases both in a horizontal and vertical plane.

5. A shallow circular soaking pit furnace for reheating ingots comprising a pit, burners through the walls of said pit at two points diametrically opposite near the top of the pit wall, said burners being directed in essentially parallel planes with the distance between their center lines being suiicient to cause considerable circulation of the combustion gases in a horizontal plane, the flame from each of said fuel burners extending into said pit a sucient distance from the adjacent wall to permit a row of ingots to be placed along the adjacent wall without danger of direct flame impingement thereon and exit ports for the waste gases directly below said burners near the bottom of the pit, the arrangement of said ingots being such that a free path is provided for circulation of hot gases both in a horizontal and vertical plane.

6. A method of heating ingots in a soaking pit having two oppositely disposed fuel burners near the top of the walls of said pit and exit ports directly below said burners which includes arranging ingots around the periphery of said pit with the exception of a space in front of each burner so that there is no danger of direct flame impingement on said ingots, and circulating gases from said burners in horizontal and Vertical planes through a path between said ingots.

7. A method of heating ingots in a soaking pit having two oppositely disposed fuel burners near the top of the walls of said pit and exit ports directly below said burners which includes arranging ingots around the periphery of said pit with the exception of a space in front of each burner so that there is no danger of direct flame impingement on said ingots, arranging other ingots in the center of said pit to form a path between the two groups of ingots and circulating hot gases from said burners in both horizontal and vertical planes through said path.

8. A method of heating ingots in a soaking pit having two oppositely disposed fuel burners near the top of the Walls of said pit and exit ports directly below said burners which includes arranging ingots around the periphery of said pit with the exception of a space in front of each burner so that there is no danger of direct ame impingement on said ingots, and controlling the velocity of flame propagation and the stack draft so that the hot gases will circulate in horizontal and vertical planes through a path between the ingots.

9. A method of heating ingots in a soaking pit having two oppositely disposed fuel burners near the top of the walls of said pit and exit ports directly below said burners which includes arranging ingots around the periphery of said pit with the exception of a space in front of each burner so that there is no danger of direct ame impingement on said ingots, arranging other ingots in the center` of said pit to form a path between the two groups of ingots, and controlling the velocity of flame propagation and the stack draft so that the hot gases will circulate in horizontal and vertical planes through said path.

10. A method of heating ingots in a soaking pit, which comprises arranging the ingots in rows in the pit so as to provide a combustion zone between the ingots, directing a flame from a burner into the furnace, and circulating the gases in a U-shaped path in a vertical plane through the said zone.

11. A method of heating ingots in a soaking pit, which comprises arranging the ingots in rows in the pit so as to provide combustion zones between the ingots, directing flames into the pit from diagonally oppositely disposed burners, and circulating the hot gases from said burners in both horizontal and vertical planes through the said zones.

RICHARD R. SNOW. 

